Serial Port Issues Preventing Purchase - Help Please

OK so I have selected the Lulzbot Mini for my next 3D printer purchase and I’m chomping at the bit to place the order yet there is just one final detail to get cleared up before ka-ching! Sold!

The issue is that my existing Printrbot Simple Metal is causing Cura to list a serial port error after running a print for some time between 15 and 45 minutes. It’s always the same error and it says this:

Recv: ok T:178.3 /0.0 B:0.0 /0.0 T0:178.3 /0.0 T1:26.4 /0.0 T2:43.2 /0.0 @:0 B@:0

Unexpected error while reading serial port: SerialException: 'read failed: [Errno 6] Device not configured' @ machineCom.pyo:_readline:576

Changing monitoring state from 'Operational' to 'Error: SerialException: 'read failed: [Err...'

Connection closed, closing down monitor

I was using a long dangly USB cord with an extension USB cord which fit loosely into the printer. So I replaced the cord with a nice short one that fit properly into the printer. I have not yet printed for enough time to know wether or not this fixed it, but if it did I’ll feel confident in buying the Mini.

Why delay a Lulzbot purchase because of an error with a Printrbot? Because the Mini can ONLY print from the serial port. There is no SD card option. I would hate to ask my family to spend all that money on a printer plus accessories only to have to tell them that I STILL cannot print. That’s the situation, advice please?


Get a raspberry pi and load astroprint. Bypass the serial port on your computer all together!

The raspberry is the way to go.

The error with the printerbot is likely a USB disconnect due to the loose/long cable. It could also be drivers in the computer OS, but those usually break completely, not half way like that.

Consider running OctoPi.

For security reasons, mainly the lack thereof, I would prefer not to put my 3D printer on the web. What are my options then, a computer dedicated to the printer? Perhaps an RPi computer without the network? Or just get an old mac? I dunno, this is a conundrum…


Octopi can be run on a LAN without internet connectivity

Check out Astroprint, where the RPi is a hotspot for the printer. Thus only the RPi is connectable to the web/local web, and only the person that know the login/password can use it.

Or at least as well as I can remember.

I second that the issue probably was/is an overly long usb cable. Long usb cables are not recommended for things to begin with as the signals can degrade or have more chance for interference. Especially when combined with a cheap usb extension cable. I certainly wouldn’t trust running a printer on a cable like that. If it’s working now i’d be confident to say that was your problem.

But i too am looking into the Raspberry Pi idea with something like Octoprint or some other such software. While i have not used a raspberry pi before or any of those types of software my understanding is that 1. like someone else said, you can use it over LAN without connecting it to the internet (this just requires you have a secure router). or 2. The Raspberry Pi is basically a small computer (presumably running some form of linux like debian), in which case the Pi could easily be set and configured to broadcast a private and secured wifi connection that only you would know the password to. The new Raspberry Pi 3 is looking awfully tempting with that built in wifi chip.

The reprap wiki says:

Drip-feed the G-codes (usually a line at a time) over a serial port (RS-232 or TTL level, often used with a USB converter) or a direct USB connection using one of the following programs on your workstation:

I got to thinking about this, seems like one could put an ESP8266 chip on either end of a cable, pair them with their unique chip IDs, and have them communicate this Drip-feed of G-codes from the computer to the printer. It would probably be necessary to use low speeds or something. So the idea is to make a sort of wifi cable. The paired chips could use mesh networking so as not to be affected by conventional wifi equipment, hence security feature.

Is this even a reasonable idea?


Well no, that is a crazy idea. Octopi work as is so I will go that route!


OctoPi is actually quite secure. First you don’t have to forward a port to expose it to the entire internet. Second, OctoPi is setup by default to provide HTTPs through a forward proxy.

Yes, Octopi is an awesome way to go!

When you order your PI-2, I would recommend getting the little camera with it.

Octoprint directly supports the camera and it’s very nice to be able to watch the progress without having to walk over to the printer!!

There are several cases for the Pi and camera over on .

I have attached pictures of the cases that I printed. Sorry, but I don’t remember the file names.


There’s a list of USB cameras that work with Octoprint. So not constrained to the RPi camera, which is a bit awkward due to the ribbon cable. If you do go with the RPi camera get a longer ribbon cable, the supplied really isn’t enough with the moving bed.

I went from the RPi camera to the Logitech C270.

cool cool and I don’t know what I’m worried about, I have you all for help if I get into trouble! Thanks in advance for that. We may end up pushing some of these expenses off to future months due to how much they inflate the base price. I was given a budget of $1200 and with all the goodies, well, it’s looking like closer to $2000. Way over budget, so if I offload a few k to future months it won’t be so bad. I agree too, the cam is a highly desired feature.


Well, the Rpi-2 is 40 bucks and the camera is 30 bucks. The SD card is (I don’t remember exactly), but I think like 10 bucks for a 16 gig. Then I think 12 bucks for the WiFi dongle.

Then, you print the cases for free. Well, almost free.

So, around a hundred bucks and you have complete remote control of your printer! Don’t forget you can also control it from your phone or pad!

Then you can do this: (This is what my camera shows as I am printing now!)

The real web interface looks much better.
The screenshot I posted is clipped and not very good quality.
The RPI cam looks MUCH better in real life.

It looks like things have changed and I will have double the budget, so I must now choose from a different set of printers. Mainly the Lulzbot Taz 5 or the Ultimaker 2+. I am sitting on the fence. A major advantage to the Taz is the build size and the higher temp of the hotend. On the other hand the Ultimaker is quieter which helps a lot because I’m in a nursing home and I print at night a lot. Also the Ultimaker has easy nozzle swapping so I can use a small nozzle for small parts and a large one for big things, plus other stuff.

I think I’m talking myself into an Ultimaker. Oh and the biggest factor of all is that both have excellent community support. Well the extra bucks have not arrived formally, so it could just be a false alarm. It’s like a battle of titans, both are champions!!!


Awesome, good luck with your choice!

I hope you post your choice and most importantly, why you made that decision!!

I can see a bigger printer in my future!


Here is the comparison chart that I created to help me make my decision:

I ended up going with the Taz 5 over the UM2+ but that could change before the final moment of purchase as I have been going back and forth a lot. What would help a lot would be if I could buy a Taz 5 with a dual print head already installed and save money and waste for not having the single head wasted by the install of the dual head. Also when is the flexydually 2.0 coming out?